Students taking the university entrance physics exam in Catalonia on 9 June faced confusion over a concept that is not included in the official curriculum. The issue came in Exercise 4 of Option A, which referred to the 'mean lifetime' of a substance, the average time a radioactive nucleus exists before disintegrating.
According to the guidelines given to teachers, that concept is explicitly excluded from the subject syllabus. Some students therefore answered using 'half-life', which is part of the curriculum, while others followed the wording of the question and used 'mean lifetime'.
The Department of Universities told VilaWeb that the question was intended to test whether students could apply the radioactive decay model and calculate how a radioactive sample evolves. On that basis, the subject committee has agreed to accept both well-formulated interpretations as correct.
The same sources said there was no error in the wording of the question, despite the mismatch between the magnitude requested and the answer shown in the official correction sheet. For more Catalonia education coverage, see our news page.
Read more official context on the university entrance exams from the Department of Universities and the PAU information page.